1. Technical Field
The invention relates to tire pressure monitoring systems (TPMS) and more particularly to tire pressure monitoring systems which provide tire location identification and are integrated with tire service life management.
2. Description of the Problem
TPMS provide for monitoring of tire pressure for tires installed on a vehicle and for alerting a driver to variation in measured pressure from desired norms. Maintaining an individual tire at its recommended pressure helps extend tire life and promotes good vehicle fuel economy. Maintaining all of the tires on a vehicle at the recommended pressures promotes vehicle stability and driver control of the vehicle. Extension of TPMS to provide tire temperature data allows more accurate measurement of pressure.
Recent developments in radio frequency identification (RFID) have provided a particularly convenient way to identify and track specific tires. RFID tags applied to tires and the use of scanners to locate the tags allows maintaining databases of tire history indexed to specific tires and allows the quick location of a tire if such is needed. RFID tags may provide data storage capability and limited sensing functions, allowing the tags to be repository for data relating to a tire's service history and to be a source of data as to internal conditions.
TPMS have typically provided tire pressure sensors mounted on the wheel rim or positioned inside a tire installed on the wheel. Tire pressure sensors may also be mounted outside of the tire on the valve stem, in place of a valve cap. Radio frequency identification (RFID) systems have been proposed for read/write tire identification. However, when a rim mounted sensor incorporates the identification feature (ID) there has been no way to guarantee that data written thereon will follow the tire to a different rim if the tire is moved. Where an inner sidewall mounted pressure sensor is used, then ID remains with a tire, but new tires must come with compatible sensors or have them installed.
Many prior art TPMS have not allowed for both permanent tire radio frequency identification and tire pressure monitoring without the removal of tires for installation or replacement of associated hardware. In TPMS that requires removal of tires since pressure sensors are often mounted to the inner surface of the rim. Since the sensor does not necessarily stay mated to the tire, tire identification information is not provided with the sensor. Systems have been proposed that provide a combination device incorporating a pressure sensor and RFID. This combination device is mounted to the inner surface of the tire itself. A battery can be incorporated for power, allowing for direct transmission of data through the tire wall to a central system controller. In still other systems, a transponder would be mounted in the wheel well which would provide power to the combined sensor/RFID device by coupled radio waves. These solutions still suffer from the necessity of removal of the tires from rims in order to install or replace components of the system.
Some prior art TPMS have provided tire ID information located the sensor/RFID package inside the tire. This requires a hand held reader or antennas be located in, or be brought into, close proximity to the wheels in order for information to be retrieved or communicated. A more recent teaching is U.S. Pat. No. 6,724,301 to Ginman et al. Ginman proposed a dual tag tire and wheel RFID system. Ginman utilized a temporary tire tag located a tire and with RF read/write capability and another wheel mounted tag with RF read/write capability. Both tags were provided with the capability of storing data pertinent to tire and wheel condition. An external RFID interrogator is used to effect sharing of data between the two RFID tags. Data is not lost due to discard or rotation of tires.